Exported enums should remember set key, not values.

[NickSw1ft]

If you change order of enum keys in script, all exported variables of this enum are going to be shifted.
E.g. in the following example if I set boo to C via editor and then change order or insert element in Foo, boo key will change.
enum Foo {A, B, C}
@export var boo: Foo = Foo.A
I would like to propose that in such cases exported variable is assigned a value corresponding to key set in editor.

[dalexeev]

This is a core issue, built-in enums also store values, not keys (so we try not to shift values). This could be solved with a new usage flag and annotation, but if I remember correctly, the built-in enums do not store keys in release builds to save space.

As a workaround, you can explicitly specify the enum values:

enum Foo {
    A = 0,
    B = 1,
    C = 2,
    # Add new values to the end, don't shift IDs!
}
@export var boo: Foo = Foo.A

or use the @export_enum annotation:

@export_enum("A", "B", "C") var boo: String = "A"

[NickSw1ft]

Thank you for suggested workarounds. I would like to point out that secong one is really awkward as it takes away the convenience of enums and editor hints. The first one is neat, but could be really confusing and clunky after a dozen of values and a couple of shiftings.

[Mickeon]

If you remember the keys instead of the values, the problem is not solved, but it is shifted to the keys. If you change the name of any key the same issue happens.
Storing the raw value is more efficient and less of a workaround (since enum values are just integers at the end of the day).

The editor should also not be trusted in predicting what has been changed and how. This is the kind of thing that some sort of refactoring tool could help manage (something that has been asked many times before).